The present age of social media and social networks offers tremendous opportunity for content publishers and advertisers to provide their content and advertisements to consumers (e.g., herein referred to as users). Content items, including advertisements, can be provided to users of a social network in various forms and contain many different pieces of information designed to attract the interests of the users. The impression that a particular item of content has on a particular social network user is of great value to content publishers, and especially to advertisers seeking to implement efficient and effective advertising strategies. As recognized by the inventors, it is important for content publishers such as advertisers to be able to differentiate among social network users based on how valuable each user is in terms of propagating content throughout one or more social networks.